How to prevent nausea and vomiting due to chemotherapy

　　Acute nausea and vomiting: usually occurs within minutes to hours of administration and peaks 5 to 6 hours after administration, but mostly resolves within 24 hours.
　　Delayed nausea and vomiting: Most often occurs after 24 hours of chemotherapy and commonly occurs with cisplatin, carboplatin, cyclophosphamide and adriamycin chemotherapy and can last for several days.
　　Anticipatory nausea and vomiting: nausea and vomiting that occurs immediately before the start of the next chemotherapy treatment after experiencing uncontrollable CINV during the previous chemotherapy treatment is a conditioned reflex, mainly due to psychiatric and psychological factors. Anticipatory nausea and vomiting is often accompanied by anxiety and depression and is associated with poor control of previous CINV, with an incidence of 18% to 57%, and nausea is more common than vomiting. Anticipatory nausea and vomiting is likely to occur in younger patients because they tend to receive more intense chemotherapy than older patients and have poorer control of vomiting.
　　Eruptive vomiting: vomiting that occurs despite prophylaxis and requires “rescue therapy”.
　　Refractory vomiting: vomiting that occurs in the next chemotherapy cycle after failure of prophylactic and/or palliative antiemetic treatment in the previous chemotherapy cycle.
　　Emetic grading of antineoplastic drugs
　　Anti-tumor drug-induced vomiting depends mainly on the emetic potential of the drug used. Generally, antineoplastic drugs can be classified into four emesis risk classes: high, moderate, low and mild, which means the incidence of emesis is >90%, 30%-90%, 10%-30% and <10% respectively if not treated with prophylaxis. The combination of multiple antineoplastic agents and multiple cycles of chemotherapy may increase the incidence of nausea and vomiting. < p="">
　　IV. Other factors associated with CINV
　　Chemotherapy drugs, regimens, and patients’ own conditions can affect the occurrence of CINV. The own emetic potential of chemotherapy drugs in the chemotherapy regimen is the most important factor in CINV; the emetic potential of each drug varies with its dose intensity, dose density, infusion rate, and route of administration.
　　The patient’s own factors associated with CINV include gender, age, history of alcohol intake, anxiety, physical status, motion sickness, underlying disease, and control of vomiting from prior chemotherapy. The control of nausea and vomiting during previous chemotherapy is a particularly important factor that may influence the occurrence of anticipatory and delayed vomiting during the current chemotherapy.
　　Nausea and vomiting occur more frequently and vomiting is more difficult to control in younger patients compared to older patients. Vomiting was more effectively controlled in patients with chronic and heavy alcohol intake (100 g of alcohol per day). Women are at higher risk of nausea and vomiting compared to men. Among the multiple factors associated with the above, the type of chemotherapy, younger age, and being female are independent risk factors for the development of CINV.
　　V. Principles of CINV treatment
　　The choice of antiemetic drugs should be based on the risk of emetics with antineoplastic agents, previous experience with antiemetics, and patient factors.
　　For multi-drug regimens, the choice of antiemetic should be based on the drug with the highest risk of emetics. Combination of several antiemetics can provide better control of nausea and vomiting, especially when highly emetic chemotherapy is used.
　　Along with the prevention and treatment of vomiting, care should be taken to avoid the adverse effects of antiemetic medications.
　　A good lifestyle can also relieve nausea/vomiting, such as eating smaller and more frequent meals, choosing healthy and beneficial foods, controlling food intake, and not eating cold or overly hot foods.
　　Other factors that may cause or aggravate nausea and vomiting in oncology patients should be noted: partial or complete intestinal obstruction; vestibular dysfunction; brain metastasis; electrolyte disorders: hypercalcemia, hyperglycemia, hyponatremia, etc.; uremia; combination with opioids; oncology or chemotherapy (e.g., vincristine), or other factors such as gastroparesis due to diabetes; psychological factors: anxiety, anticipatory nausea/vomiting, etc. vomiting, etc.
　　VI. Prevention of CINV
　　Re-evaluate the risk of drug induced emesis, disease status, complications and treatment; pay attention to various non-chemotherapy related causes of emesis such as brain metastases, electrolyte disturbances, intestinal obstruction, tumor invasion into the intestine or other gastrointestinal abnormalities, or other comorbidities. Revisit the last ineffective antiemetic regimen and consider changing antiemetic medications.
　　Determine the best treatment option to give to the patient for the risk of emetics. If oral administration is difficult to achieve in a patient with emesis, administer the medication rectally or intravenously; choose a combination of medications if necessary, with the option of a different regimen or a different route.
　　Consider adding lorazepam or alprazolam to the treatment regimen.
　　Consider adding olanzapine or using metoclopramide instead of a 5-HT3 receptor antagonist or adding a dopamine antagonist to the treatment regimen.
　　Ensure adequate fluid supply, maintain water-electrolyte balance, and correct acid-base imbalance.
　　In addition to 5-HT3 receptor antagonists, other medications may be chosen as adjunctive therapy: including lorazepam, dronabinol, cannabisol, haloperidol, olanzapine, scopolamine, prochloraz and promethazine (all 2A recommendations).
　　VIII. Treatment of anticipatory nausea and vomiting
　　As the number of chemotherapy increases, the incidence of anticipatory nausea and vomiting often tends to increase. Anticipatory nausea and vomiting is more difficult to treat once it occurs, so the best treatment is to prevent its occurrence by controlling the occurrence of acute and delayed nausea and vomiting during each cycle of chemotherapy whenever possible. Behavioral therapy, particularly progressive muscle relaxation training, systematic desensitization therapy, and hypnosis, can be used to treat anticipatory nausea and vomiting. Benzodiazepines can reduce the occurrence of anticipatory nausea and vomiting, but their effectiveness tends to decrease with the continuation of chemotherapy. Available drugs include alprazolam and lorazepam.
　　IX. Management of adverse reactions and complications
　　Constipation
　　Constipation is the most common adverse effect of 5-HT3 receptor antagonists. Impaired intestinal secretion and peristaltic function caused by antiemetic drugs is the most common clinical cause of constipation. In addition, chemotherapeutic drugs interfere with gastrointestinal function, impaired cortical function, impaired consciousness and vegetative nerve dysfunction can cause constipation.
　　Treatment: (1) Dietary and activity guidance: drink more water, eat more vegetables, fruits and foods containing more fiber. Encourage the patient to move more to promote bowel movement and prevent constipation. (2) Massage: do circular massage in the patient’s abdomen in the direction of colonic travel. Do deep breathing to exercise the muscles and increase the power of bowel movement. (3) Acupuncture: acupoints such as tianshu, sesanli, zhiyang, and sanyinjiao; or moxibustion at upper juxu, nei ting, and sesanli. (4) Pharmacological control: laxatives to lubricate the intestinal tract, such as honey, fragrant oil or liquid paraffin oil; Chinese herbs, such as Ma Ren Wan, Liu Wei Di Huang Wan and Si Mo Tang; or the use of open plug, glycerin suppositories, and soap bars for anal plugs. (5) If the medication is ineffective, the fecal mass can be pulled out directly through the anus in the rectum, or low-pressure enema with warm saline, but it should be used with caution for those with increased intracranial pressure.
　　Headache
　　Headache is a common adverse effect of 5-HT3 receptor antagonists. Treatment: (1) For headache with infrequent attacks and not very intense, use heat compresses. (2) Massage: Stroke the forehead and rub the temples; do dry-cleaning movements. (3) Acupuncture: acupuncture points such as Sun, Baihui, Fengfu and Fengchi; or moxibustion points such as Qihai, Feisanli and Sanyinjiao. (4) Medication: give antipyretic and analgesic drugs during headache attack; ergotamine caffeine is available for severe cases.
　　Environment and diet Poor air circulation, high or low temperature and humidity, bad odor, noise and crowded and cluttered space in the ward can stimulate patients and induce or aggravate nausea and vomiting. Excessive smell of food, greasy, too hot as well as too cold food can cause nausea and vomiting; sweet food is also often a factor that causes vomiting. Therefore, to create a pleasant environment, choose to play soft, slow melody, low frequency and patient’s favorite light music in the ward, encourage patients to read, watch TV or engage in activities of interest, etc., can divert patients’ attention, help stabilize emotions and reduce nausea and vomiting symptoms. During radiotherapy, it is advisable to have a reasonable diet, appropriately light, with few meals, 5 to 6 times a day, and more meals at the time of day when nausea is least likely to occur (mostly in the early morning). Drink as little water as possible before and after eating. Do not lie down immediately after the meal to avoid food reflux and nausea. Avoid alcohol, sweet, greasy, spicy and fried foods. Eat less tryptophan-rich foods, such as bananas, walnuts and eggplants. In addition, health education for the patient’s family and surrounding people should be actively done to form a good social support system and to comfort and encourage the patient more.
　　Nutritional support Strengthen dietary care and actively promote the importance of eating and increasing nutrition to patients. According to the patient’s hobbies, work out a diet plan with the patient and family members, and give a light, easily digestible liquid or semi-liquid diet with high nutrition and vitamins to reduce the time of food retention in the stomach. Food should be warm and moderate. Fruits that are acidic can relieve nausea. Modify your diet by eating smaller and more frequent meals and avoid eating 1 to 2h before and after treatment. Avoid contact with people who are cooking or eating to reduce irritation. When vomiting is frequent, abstain from eating and drinking for 4 to 8h, which can be extended to 24h if necessary, and then slowly enter a liquid diet. Avoid drinking large amounts of water. Broth, vegetable broth and juice can be used to ensure the body’s nutritional needs and maintain electrolyte balance.
　　Other treatments Extreme psychological stress and anxiety, fear and tension can stimulate vomiting through the brain and brainstem, and tumor patients are prone to pessimism and disappointment and lose confidence in treatment, so it is important to do a good job of psychological guidance and psychological care. During the treatment process, we must understand the disease, be familiar with the treatment plan, grasp the patient’s psychological state, give reasonable guidance and stabilize the patient’s emotion. Psychological and social factors are significantly correlated with the survival quality and survival period of cancer patients. Therefore, psychological treatment for cancer patients is particularly important and is receiving more and more attention.
　　Brief introduction of commonly used clinical antiemetic drugs
　　(A) 5-HT3 receptor antagonists
　　Chemotherapy can release 5-HT3 from chromophores in the digestive tract and bind to 5-HT3 receptors in the vagus nerve endings of the digestive tract mucosa, which in turn stimulates the vomiting center to cause vomiting. 5-HT3 receptor antagonists exert antiemetic effects by binding to 5-HT3 receptors in the digestive tract mucosa. The various spermidine drugs have similar antiemetic effects and safety profiles and are interchangeable. The efficacy and safety of oral and intravenous medications are similar. Common adverse effects include mild headache, transient asymptomatic transaminase elevation, and constipation. It is important to note that increasing the dose of 5-HT3 antagonists does not increase efficacy, but may increase adverse effects, even serious ones (prolonged QT interval).
　　?　　Haloperidol, a butylphenolic antipsychotic, blocks dopamine receptors in the brain, mainly for antipsychotic and anxiolytic effects, also has a strong antiemetic effect, used for the relief of chemotherapy-induced nausea and vomiting, 1 to 2 mg orally every 4 to 6 hours, the main adverse effects are extrapyramidal reactions.
　　Olanzapine, an atypical antipsychotic, has affinity for a variety of receptors, including 5-HT2 receptors, 5-HT3 receptors, 5-HT6 receptors, dopamine D1, D2, D3, D4, D5, D6 receptors, adrenergic and histamine H1 receptors. It is used as a relief treatment for chemotherapy-induced nausea and vomiting, and is administered orally 2.5 to 5 mg twice a day.
　　Lorazepam, also known as chlorohydroxystrobin, is an anxiolytic and a moderately effective benzodiazepine sedative-hypnotic. In the prevention of vomiting caused by low to moderately high emetic chemotherapeutic drugs and in relief therapy, 0.5-2 mg orally or intravenously or sublingually every 4-6 hours.
　　Alprazolam, benzodiazepine CNS depressants for anticipatory nausea and vomiting, 0.5 to 2 mg TID orally.
　　(F) phenothiazines
　　